INSQ(9F) Kernel Functions for Drivers INSQ(9F)
NAME
insq - insert a message into a queue
SYNOPSIS
#include <sys/stream.h>
int insq(
queue_t *q,
mblk_t *emp,
mblk_t *nmp);
INTERFACE LEVEL
Architecture independent level 1 (DDI/DKI).
PARAMETERS
q Pointer to the queue containing message
emp.
emp Enqueued message before which the new message is to be
inserted.
mblk_t is an instance of the
msgb(9S) structure.
nmp Message to be inserted.
DESCRIPTION
The
insq() function inserts a message into a queue. The message to be
inserted,
nmp, is placed in
q immediately before the message
emp. If
emp is
NULL, the new message is placed at the end of the queue. The
queue class of the new message is ignored. All flow control
parameters are updated. The service procedure is enabled unless
QNOENB is set.
RETURN VALUES
The
insq() function returns
1 on success, and
0 on failure.
CONTEXT
The
insq() function can be called from user, interrupt, or kernel
context.
EXAMPLES
This routine illustrates the steps a transport provider may take to
place expedited data ahead of normal data on a queue (assume all
M_DATA messages are converted into
M_PROTO T_DATA_REQ messages).
Normal
T_DATA_REQ messages are just placed on the end of the queue
(line 16). However, expedited
T_EXDATA_REQ messages are inserted
before any normal messages already on the queue (line 25). If there
are no normal messages on the queue,
bp will be
NULL and we fall out
of the
for loop (line 21).
insq acts like
putq(9F) in this case.
1 #include <sys/stream.h>
2 #include <sys/tihdr.h>
3
4 static int
5 xxxwput(queue_t *q, mblk_t *mp)
6 {
7 union T_primitives *tp;
8 mblk_t *bp;
9 union T_primitives *ntp;
10
11 switch (mp->b_datap->db_type) {
12 case M_PROTO:
13 tp = (union T_primitives *)mp->b_rptr;
14 switch (tp->type) {
15 case T_DATA_REQ:
16 putq(q, mp);
17 break;
18
19 case T_EXDATA_REQ:
20 /* Insert code here to protect queue and message block */
21 for (bp = q->q_first; bp; bp = bp->b_next) {
22 if (bp->b_datap->db_type == M_PROTO) {
23 ntp = (union T_primitives *)bp->b_rptr;
24 if (ntp->type != T_EXDATA_REQ)
25 break;
26 }
27 }
28 (void)insq(q, bp, mp);
29 /* End of region that must be protected */
30 break;
...
31 }
32 }
33 }
When using
insq(), you must ensure that the queue and the message
block is not modified by another thread at the same time. You can
achieve this either by using STREAMS functions or by implementing
your own locking.
SEE ALSO
putq(9F),
rmvq(9F),
msgb(9S) Writing Device Drivers STREAMS Programming GuideWARNINGS
If
emp is non-
NULL, it must point to a message on
q or a system panic
could result.
March 23, 2009 INSQ(9F)
